Shaped metal tubes are desirable for use in automotive body assemblies due to their strength and relatively low weight. In constructing automotive body assemblies that use bent, hydroformed tubes or the like, it is sometimes necessary to join a body member to a structural tube, wherein the body member is composed of a first material and the structural tube is composed of a dissimilar, second material.
However, it is often difficult to use traditional spot welding, riveting, or bolting practices to make sheet-to-tube assemblies. It has been difficult, if not impossible, to reliably spot weld dissimilar materials such as ferrous to non-ferrous materials, particularly steel to aluminum. Such materials have significantly different melting points, which tend to render the materials incompatible for traditional resistance welding techniques, wherein the first material is attempted to be welded directly to the second material.
Moreover, riveting and bolting such dissimilar materials tends to be undesirable for several reasons. First, the tensile strength of a rivet joint or a bolt joint is relatively low compared to a weld joint. Second, extensive and tedious experiments must be conducted to determine the optimal die and rivet for a particular selection of material composition and thickness. Third, many riveting and bolting operations are prohibitively complex. For example, riveting operations require not only a punch to drive a head on the rivet, but also require a backup die to deform a shank of the rivet, wherein the backup die can be extremely difficult position deep within a tubular part. Also, bolting operations tend to involve messy milling and tapping operations and/or difficult bolt and nut assembly operations.
Thus, it is an object of the present invention to provide a method of joining dissimilar materials for an automotive body assembly or the like. It is a further object of the present invention to provide a method of joining dissimilar materials where the joint is robust and will contribute to the structural integrity of the assembly.